EA038638B1 - Method of natural gas supply - Google Patents

Abstract

The invention relates to the gas industry, in particular, to methods of natural gas supply to consumers, and to the liquified natural gas production technology. Gas from a gas field is purified and prepared for transportation, fed to the main pipeline, additionally cleaned. A portion of gas passing through a natural gas liquefaction plant, operating in parallel to a gas distribution station, is liquefied. The liquefied gas is collected in a cryogenic vessel, transferred to a transport tank and delivered to a consumer, into a service tank. In order to avoid energy consumption, natural gas is converted to a liquid aggregate state due to additional work of natural gas compression using a well known method based on the Joule-Thomson effect or on expander cryogenic cycle. A portion of liquefied gas from the service tank is fed to charging evaporators; downstream of the evaporators, the heated and considerably expanded gas is fed to the service vessel cavity above the liquid surface, which ensures the displacement of the liquid into an evaporator-regasifier. The liquid at a pressure exceeding the pressure of the distribution network is gasified and heated in the evaporator-regasifier by the heat of the environment. The technical result that is the purpose of this invention is the creation of a simplified and low cost method for natural gas supply to consumers.

Description

The invention relates to the gas industry, specifically to the technology for the production and use of liquefied natural gas (hereinafter referred to as LNG), as well as to methods of gas supply to consumers with natural gas (hereinafter referred to as LPG).

There is a known method of gas supply (for example, ed. St. No. 832241, ed. St. No. 1634946), when the gas extracted from the field is cleaned of mechanical particles and unwanted impurities, then transported through the main pipeline to the place of consumption. At the same time, to maintain a constant pressure of the transported gas, required for efficient gas transportation, and to compensate for hydraulic losses from the resistance of the pipeline along the length, the gas is compressed using compressors (gas pumping units) of compressor stations, spending for this electrical energy or heat energy obtained from burning a part transported gas. When the main gas pipeline approaches the place of consumption - a settlement or a manufacturing enterprise, the SG pressure is reduced to safe values (up to 0.6 and 1.2 MPa, respectively) and it is fed into the distribution pipeline of the gas distribution network, through which it is delivered to each end consumer ... The pressure is reduced at the regulators of the gas distribution station (hereinafter referred to as the gas distribution station) by throttling, while the potential energy of the compressed gas, imparted to it by the compressor station blowers, turns into irreversible thermodynamic losses. These losses reduce the energy efficiency of gas transportation, and, consequently, of this method of gas supply as a whole. Another disadvantage of this method is the need to lay a main gas pipeline or a gas pipeline branch to each gasification facility, which, as a rule, requires high capital costs and can be justified only by high and constant gas consumption. Gasification of consumers with low costs and variable, for example seasonal, consumption is not economically feasible.

There is also known a method of gas supply to settlements (RF patent No. 2458283, priority date 07/05/2011), which differs from the first in that the produced GHG is liquefied in the field after preliminary purification from mechanical particles and unwanted impurities. Then LNG is pumped in a known way into methane tankers, delivered in tankers to the terminal close to the place of consumption, pumped from the cryogenic vessels of the tanker to the cryogenic isothermal storage facilities of the terminal, then LNG is supplied by means of cryogenic pumps to evaporators-regasifiers, in which LNG is heated by ambient temperature, evaporating and heating to a temperature close to the ambient temperature, it is heated to a temperature acceptable for further supply to the gas pipeline due to electricity or heat from the combustion of a part of the regasified gas in heat exchangers. Further, the gas is transported through the main pipeline and supplied to the consumer through the distribution pipeline, as in the first method. The purpose of this method is to reduce capital costs for the construction of a main pipeline, as well as to reduce energy costs for transportation (compression of GHG) in relation to the above-described method, as well as the possibility of diversifying GHG supplies in the event of a change in consumer demand for a primary energy carrier. The disadvantage of this method is that a significant amount of energy must be spent to liquefy GHGs. The theoretical minimum work of methane liquefaction is 0.307 kWh / kg, and the real one, taking into account the irreversibility of cryogenic cycles, is 0.6-1 kWh / kg. Further, an equivalent amount of energy must be supplied to the LNG during its regasification and heating. The following disadvantages of the first remain in this method: irreversible thermodynamic losses during reduction at the gas distribution station, the need to lay a main gas pipeline or a gas pipeline branch from the terminal to each gasification facility.

The technical result to which the invention is directed is the creation of a simplified and cheap method of gas supply to consumers with natural gas.

This result is achieved by the fact that gas from the field is purified and prepared for transportation, supplied to the main pipeline, additionally purified, part of the gas passing through the NGL liquefaction complex operating in parallel with the gas distribution station is liquefied, liquefied gas is accumulated in a cryogenic vessel, poured into a transport container and delivered to the consumer in the supply container. In order to eliminate energy consumption, the GHG is converted into a liquid state of aggregation due to the excess work on compression of the GHG in a known manner based on the Joule-Thomson effect or on the expander cryogenic cycle. For the same purpose, a part of the liquefied gas from the supply container is fed to the pressurization evaporators, after which the heated and greatly increased in volume gas is fed into the cavity of the supply container above the liquid mirror, which ensures the displacement of the liquid into the evaporator-gasifier. The liquid at a pressure higher than the pressure in the distribution network is gasified and heated in the evaporator-regasifier due to the heat of the environment.

In this method, the supply container can be located both near the place of LNG production and storage, and at a remote location, and a transport container can also be used as a supply container.

Also, in areas with a cold climate, a heat exchanger can be included in the process line that heats the compressed steam generator leaving the atmospheric evaporator (aka evaporator-regasifier) to a temperature higher than the ambient temperature.

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In addition, a part of the gas flow used to obtain cold in the liquefaction complex can also be used to supply gas to consumers supplied from the gas distribution station.

The claimed invention is illustrated by a drawing, which shows its functional diagram.

According to the above diagram, the objects participating in the implementation of the method according to the invention include a field - 1, a main gas pipeline - 2, compressor stations - 3, a gas distribution station - 4, a NGL liquefaction complex - 5, an LNG storage facility - 6, consumable tanks - 7, methane carriers - 8, pressurized evaporators - 9, evaporators-regasifiers - 10, consumers: industrial 11 and social and cultural facilities 12.

The method according to the invention is carried out as follows. Gas from the field 1 is cleaned and prepared for transportation, fed into the main gas pipeline 2, along which compressor stations 3 are installed to ensure a given flow rate of the transported SG and its optimal pressure. At the entrance to the GDS 4 on the supply pipeline, the flow is divided into two parts. A part is sent to GDS 4, and a part (the volume of which is calculated from the need, but not more than the values that allow the GDS equipment to operate in normal modes) is sent to the GDS liquefaction complex 5, which operates in parallel with the GDS of the main gas pipeline. Getting to the liquefaction complex 5, part of the GHG is transferred to a liquid state of aggregation due to the excess work on GHG compression, produced by the gas pumping stations to ensure its pipeline transport from the place of production to the place of consumption. In this case, the excess energy of the GHG flow is converted into heat (cold) due to the Joule-Thomson effect or on adiabatic expansion machines (expanders), and a part of the flow used to obtain cold at the exit from the technological cycle is a network gas and is used to supply gas to consumers. ... With a decrease in pressure and temperature, a part of the SG stream passing through the SG 5 liquefaction complex turns into a liquid state of aggregation. Part of the GHG intended for liquefaction is cleaned of mechanical particles, moisture, carbon dioxide and other undesirable impurities.

LNG is a cryogenic liquid and has a specific gravity of approximately 600 times that of a NG under standard conditions. LNG is accumulated in a cryogenic vessel (storage 6) at the NG liquefaction complex 5, where it is stored at low and medium pressure (from 0.1 to 16 kgf / cm ² ). From storage 6, LNG is poured into a cryogenic insulated supply tank 7 of the required capacity. Moreover, the supply tank 7 can be located both near the place of receipt and storage of LNG, and at a distance - at the place of consumption of compressed NG. The high density of the cryogenic liquid, the small volume it occupies, in comparison, for example, with compressed SG, and the almost complete absence of ballast gas make it possible to efficiently deliver LNG to the place of SG consumption into the supply tank 7 using methane carriers 8. Part of the LNG is supplied from the supply tank 7 into the pressurization evaporators 9 of the LNG regasification complex, where it evaporates, heats up, greatly increasing in volume, and is fed into the cavity of the supply container 7 above the liquid mirror (into the vapor pad), due to which the pressure in the supply container increases, displacing the liquid into the evaporator-regasifier 10. The liquid at a pressure higher than the pressure in the distribution network is gasified and heated in the evaporator-regasifier 10 to a temperature close to the ambient temperature. Evaporation of a cryogenic liquid (regasification) and heating to a temperature close to the ambient temperature is carried out due to the heat of the environment. Thus, the most significant part of the work on GHG for LNG production and further supply to the distribution network to industrial facilities 11 and social and cultural facilities 12 is carried out without additional energy consumption - the energy of the main GHG flow is used at the pressure drop of the GDS during liquefaction (excessively perfect work on gas transport) and the heat of the environment during regasification. Energy from external sources is used to power auxiliary systems of technological equipment for LNG production (lubrication systems, lighting, security systems, heating and lighting of workplaces). At the same time, the energy expended from the outside for the liquefaction of GHG is approximately 100 times less than the energy required for other methods (0.007 versus 0.6 ... 1 kWh / kg).

If necessary, a gas heater (heat exchanger) is connected to the process line, which heats the compressed SG leaving the atmospheric evaporator (evaporator-gasifier) to the temperature required for supply to the distribution network, which exceeds the ambient temperature (for example, up to + 5 ° C), which required in cold climates.

Claims (5)

CLAIM 1. The method of gas supply with natural gas, in which gas from the field is purified and prepared for transportation, fed into the main pipeline, additionally purified, part of the gas passing through the natural gas liquefaction complex operating parallel to the gas distribution station is liquefied, liquefied gas is accumulated in a cryogenic vessel, poured into a transport container and delivered to the consumer in a supply container, characterized in that natural gas is converted into a liquid aggregate state due to excess work on compressing natural gas from - 2 038638 in a well-known way based on the Joule-Thomson effect or on the expander cryogenic cycle, part of the liquefied gas from the supply tank is fed to the pressurization evaporators, after which the heated and greatly increased in volume gas is fed into the cavity of the supply tank above the liquid surface, which contributes to the displacement liquid in the evaporator-regasifier, the liquid at a pressure higher than the pressure in the distribution network is gasified and heated in the evaporator-regasifier due to the heat of the environment. 2. The method of gas supply with natural gas according to claim 1, characterized in that the supply container can be located both near the place of production and storage of liquefied natural gas, and at a remote location. 3. The method of gas supply with natural gas according to claim 1, characterized in that a heat exchanger is included in the process line, with the help of which the compressed natural gas leaving the evaporator-gasifier is heated to a temperature exceeding the ambient temperature. 4. The method of gas supply with natural gas according to claim 1, characterized in that part of the gas flow used to obtain cold in the liquefaction complex is also used for gas supply to consumers supplied from the gas distribution station. 5. The method of gas supply with natural gas according to claims 1 and 2, characterized in that a transport container can be used as a supply container.